Fibrosis is a proliferation of fibrous connective tissue.
The process occurs normally in the formation of scar tissue to replace normal tissue lost through injury or infection. It is an abnormal condition in which fibrous tissue spreads over or replaces normal smooth muscle or other normal organ tissue.
Fibrosis is most common in the heart, lung, peritoneum, and kidney.
Pulmonary fibrosis (also called idiopathic pulmonary fibrosis [IPF], interstitial diffuse pulmonary fibrosis, or fibrosing alveolitis) is an inflammatory lung disorder characterized by abnormal formation of fibrous tissue between the alveoli.
The characteristics of idiopathic pulmonary fibrosis (IPF), a progressive and fatal lung disease, are inflammation of the alveoli (spaces in the lungs where gases are exchanged) damage to lung tissues, and progressive interstitial fibrosis (hardening of tissues).
Damage to the lining of the lungs (epithelium) is caused by the increased release of oxygen radicals (oxidants). The oxidant-antioxidant imbalance is made worse because there is also a deficiency of the epithelial lining fluid glutathione.
Cryptogenic fibrosing alveolitis is the most common diagnosis of patients presenting with interstitial lung disease. Patients usually present in the sixth or seventh decade. The disease is more common in men than in women.
The cause is unknown. Scleroderma, a blood factor associated with rheumatoid arthritis, may be involved.
Manifestations include progressive dyspnea and coughing that may not ease bronchial irritation. Rapid, shallow breathing and coughing occur with moderate exercise. The skin may appear cyanotic, and fingers or toes may become clubbed.
Loss of appetite and weight, fatigue, fever, weakness, and vague chest pains are common. Infections occur easily, and untreated individuals develop complications that include emphysema, pulmonary infections, or cardiac disease. Imaging techniques monitor progressive lung changes.
High doses of oral corticosteroids (e.g., prednisone, 40 to 80 mg daily) are the usual treatment. Cytotoxic drugs such as cyclophosphamide and azathioprine have also been used.
Controlled clinical trials have not demonstrated any beneficial effect of therapy, but clinical experience with these drugs suggests that about 20 percent of patients will improve.
The response to corticosteroids is better in patients with more inflammation and less fibrosis noted on lung biopsy. Relentless progression of the disease with eventual respiratory insufficiency is the rule, and the average survival time is about four years. Lung transplantation for highly selected patients with end-stage pulmonary fibrosis has been reported.